Another excellent Wikipedia page:
https://en.wikipedia.org/wiki/Particle_swarm_optimization
Here's a good 1-D optimization problem, it lets you choose different functions (most of them difficult) and change some of the PSO parameters
http://madflame991.blogspot.com/p/particle-swarm-optimization-demo-1.html
I'm not sure that I trust this one, but it is PSO in 2D. It didn't work in Chrome, but did in Firefox. (fixing it might make a good project)
https://www.cs.drexel.edu/~introcs/Fa13/labs/L9-loopsAI/particleSwarm.html
Some notes on PSO including a paper written by prior students in this class